Japanese Unexamined Patent Application Publication No. 2009-154338 (Patent Document 1), Japanese Unexamined Patent Application Publication No. 2009-250364 (Patent Document 2), and Japanese Unexamined Patent Application Publication No. 2011-152729 (Patent Document 3) disclose a method of manufacturing a resin rotator, in which a reinforcement fiber base material (molding material) is formed on the outer peripheral portion of a bushing using slurry obtained by mixing reinforcement short fibers and water. In the methods described in the documents mentioned above, the slurry is poured into a cylindrical die that houses a metal bushing, water is removed from the slurry such that reinforcement fibers will not leak out but be aggregated around the bushing to form an aggregate, and thereafter the aggregate is compressed to form a reinforcement fiber substrate (molding material). In the method described in Japanese Unexamined Patent Application Publication No. 2011-152729 (Patent Document 3), in particular, a slurry diffusion member is disposed at the center of the cylindrical die. The slurry diffusion member includes a conical slurry diffusion portion provided at an upper end portion thereof. Therefore, it can be expected that the slurry can be poured into the cylindrical die without significant fluctuations by pouring the slurry into the molding die onto the slurry diffusion portion from above the slurry diffusion portion.